1. Field of the Invention
The present invention generally relates to accumulator filter units for use in automotive air-conditioning systems. More particularly, the present invention relates to a unique oil filter unit attached to an aperture in a bight portion of an outlet tube of an accumulator dehydrator.
2. Description of the Prior Art
Certain types of air conditioning systems require the use of an accumulator dehydrator as part of the air-conditioning system. The accumulator dehydrator is located just before the compressor and operates to ensure that no liquid refrigerant fluid is sent to the compressor which may cause slugging of the compressor. Accumulator dehydrators also commonly include some means for entraining oil in the gaseous refrigerant fluid sent to the compressor so the oil can lubricate the parts of the compressor. Typically, an oil filter is used in the accumulator for filtering debris from the oil prior to the oil being entrained in the gaseous refrigerant fluid returned to the compressor.
It is well known in the art to have the oil filter connected on an aperture in a conduit, such as an outlet tube of the accumulator dehydrator. However, various other types of oil filters and devices have been proposed for entraining oil in the gaseous refrigerant fluid returning to the compressor.
U.S. Pat. No. 4,316,622, to Nelson, incorporated herein by reference, discloses a conduit clamp assembly for maintaining a secure connection of an oil filter to a conduit by means of a compressive force clamp. The oil filter assembly is unitary with the clamp. However, the oil filter assembly disclosed in the Nelson reference has a flexible extension or nipple which is inserted into the aperture in the conduit as a passageway for the lubricating oil to be entrained in a gaseous refrigerant fluid flowing through the conduit. The extension or nipple of the oil filter assembly of the Nelson reference has a tendency to become crushed upon insertion into the apertured conduit and is unreliable. If this oil filter unit ceases to entrain oil in the gaseous refrigerant fluid, the compressor will not be lubricated and will operate inefficiently and eventually become inoperative, necessitating replacement and a complete repair of the air-conditioning system at significant expense.
U.S. Pat. No. 3,872,689, to Bottum, provides an oil filter element completely surrounding a bight portion of the outlet tube; the oil filter element covers an aperture located in the bight portion of the outlet tube. The filter is designed merely to filter fluid before it passes through the aperture. The '689 design requires a significant amount of oil in the system because of the design of the filter and location of the aperture thereby adding significantly to the overall cost of the accumulator.
U.S. Pat. Nos. 4,331,001, to Jones, and 4,509,340, to Mullally et al., disclose a pick-up tube that extends vertically from the bottom of an accumulator canister. A filter unit is attached to the inlet end of the pick-up tube located in the bottom of the accumulator. The pick-up tube of these references extends upward to an opening in an inlet end of an outlet tube located near the top of the accumulator canister. In order for the pick-up tube to reach the outlet tube located at the top of the accumulator, the pick-up tube must be made extremely long. The lengthy nature of these pick-up tubes requires the tubes be bent to pass a desiccant material and reach the inlet end of the outlet tube, which adds significantly to cost. In addition, a seal is required at the outlet tube opening to prevent any leaking of oil and liquid refrigerant. Most significantly, the design of the '001 and '340 references requires that a very high venturi pressure be created to entrain oil in the gaseous refrigerant fluid returned to the compressor. These configurations operate very poorly and add unnecessary cost and complexity to the accumulator assembly and will not work in some prior art air-conditioning systems.
Thus, there is still a need to improve upon the oil filter assembly for use in an accumulator of an air-conditioning system to provide a reliable connection to an apertured conduit for an oil filter assembly which is efficient in operation of the air-conditioning system, without adding unneccessary cost and complexity to the accumulator assembly.